US Streetlights Are Turning Purple

Post by pxc » Fri, Jun 20, 2025, 7:40 PM UTC

adgjlsfhk1 wrote: post #118

pxc wrote: post #74

Earlier quoted context omitted.

Higher contrast isn't strictly better. Street lights where I live are deliberately sparse to limit light pollution, but this means that some of them are sometimes too bright— since the whole road isn't suffused evenly with light, very bright lights are somewhat blinding, especially to light sensitive people.

LEDs are much better for this since you can get tailored light thrown by angle to even out the lighting a lot more

Thanks for sharing this! I don't know much about light and didn't realize such a thing would possible. This seems like a great technique for cities like mine that want to limit light pollution.

Post by davidmurdoch » Sat, Jun 21, 2025, 3:08 PM UTC

worik wrote: post #117

davidmurdoch wrote: post #76

Earlier quoted context omitted.

I don't understand, you prefer the new LED lights but also like reduction in light pollution? The LEDs way brighter, so I'd think you'd prefer older lights. I'd guess about 20% of the lights in and around Orlando are purple now. Maybe the heat and UV makes it worse here?

Modern LEDs direct more of their light down, less up to the sky, so yes, much less light pollution Also they are better suited to their job so need less light. Sodium lights are nowhere near as flexible so are worse, mostly, on both counts

They're definitely far far brighter. Here a photo of an old sodium vapor lamp next to a (failing) LED near me: https://photos.app.goo.gl/vwidbJUmG997VLRN7

As far as directional lighting patterns go, that's a matter of the lamp design. Sodium vapor could be housed in a reflector that directs nearly all of it's light downwards.

I'm not against LED technology being used though, just the rampant failing LEDs and the obnoxious brightness & color they produce. Also not fond of the futuristic looking light pole design they seem to always use.

For astrophotography, sodium vapor's color cast is very easy to filter out, whereas the broad spectrum LEDs are not, especially when they don't all emit the same frequencies.

Re: US Streetlights Are Turning Purple

Re: US Streetlights Are Turning Purple